The present invention relates to titanium oxide, which exhibits a superior photocatalytic activity under irradiation of not only an ultraviolet light but also a visible light; a photocatalyst comprising said titanium oxide as a catalyst component; and a photocatalytic coating agent comprising said photocatalyst and a solvent.
Titanium oxide is known as a substance exhibiting an oxidation activity or reduction activity under light irradiation. Hereinafter, such a substance is referred to as a photocatalyst. A photocatalyst containing said titanium oxide is available commercially. When such a photocatalyst is contacted with, for example, bad-smelling substances present in a living space and working space, or undesired substances such as organic solvents, agricultural chemicals and surface active agents present in water, said bad-smelling substances or undesired substances can be decomposed.
However, said commercially available photocatalyst cannot exhibit a superior photocatalytic activity under visible light irradiation, although it can exhibit a superior photocatalytic activity under ultraviolet light irradiation.
Accordingly, an object of the present invention is to provide titanium oxide, which exhibits a superior photocatalytic activity under irradiation of visible light as well as ultraviolet light.
Another object of the present invention is to provide a photocatalyst comprising said titanium oxide as a catalyst component.
A further object of the present invention is to provide a photocatalytic coating agent comprising said photocatalyst and a solvent.
The present inventors have undertaken extensive studies about a photocatalyst. As a result, the present inventors have found a specific titanium oxide, which exhibits a superior photocatalytic activity under irradiation of visible light as well as ultraviolet light. And thereby the present invention has been obtained.
The present invention provides titanium oxide having a value of an index X1 calculated by the following equation (I) of not more than about 0.90, and a value of an index Y1 calculated by the following equation (II) of not less than about 0.075,
X1=B1/A1xe2x80x83xe2x80x83(I)
Y1=D1/C1xe2x80x83xe2x80x83(II)
wherein, as to the equation (I), A1 and B1 stand for respective half-widths of peaks, which are obtained by the process consisting of the steps:
(i) analyzing titanium oxide eight times according to an X-ray photoelectron spectroscopy,
(ii) obtaining an integrated spectrum of an electron state of titanium with respect to the above first analysis and the second analysis,
(iii) obtaining a half-width, A1, of a peak within a binding energy range of from 458 eV to 460 eV with respect to the integrated spectrum obtained in the above step (ii), and
(iv) carrying out the same steps as the above steps (ii) and (iii) with respect to the above seventh analysis and the eighth analysis to obtain a half-width, B1, of a peak, and
as to the equation (II), C1 stands for an integrated value of absorbance within a wavelength range of from 250 nm to 550 nm in measurement of an ultraviolet-visible diffuse reflection spectrum of titanium oxide, and D1 stands for an integrated value of absorbance of titanium oxide within a wavelength range of from 400 nm to 550 nm.
Further, the present invention provides titanium oxide having a value of an index X1 calculated by the following equation (I) of not more than about 0.90, a value of an index Y1 calculated by the following equation (II) of not less than about 0.075, and a value of an index Z1 calculated by the following equation (III) of not less than about 0.75,
X1=B1/A1xe2x80x83xe2x80x83(I)
xe2x80x83Y1=D1/C1xe2x80x83xe2x80x83(II)
Z1=Y1xc3x97E1xe2x80x83xe2x80x83(III)
wherein, as to the equation (I), A1 and B1 stand for respective half-widths of peaks, which are obtained by the process consisting of the steps:
(i) analyzing titanium oxide eight times according to an X-ray photoelectron spectroscopy,
(ii) obtaining an integrated spectrum of an electron state of titanium with respect to the above first analysis and the second analysis,
(iii) obtaining a half-width, A1, of a peak within a binding energy range of from 458 eV to 460 eV with respect to the integrated spectrum obtained in the above step (ii), and
(iv) carrying out the same steps as the above steps (ii) and (iii) with respect to the above seventh analysis and the eighth analysis to obtain a half-width, B1, of a peak; as to the equation (II), C1 stands for an integrated value of absorbance within a wavelength range of from 250 nm to 550 nm in measurement of an ultraviolet-visible diffuse reflection spectrum of titanium oxide, and D1 stands for an integrated value of absorbance of titanium oxide within a wavelength range of from 400 nm to 550 nm; and as to the equation (III), E1 stands for a crystallite size of titanium oxide.
Still further, the present invention provides titanium oxide having a value of an index X1 calculated by the following equation (I) of not more than about 0.90, a value of an index Y1 calculated by the following equation (II) of not less than about 0.075, a value of an index Z1 calculated by the following equation (III) of not less than about 0.75, and a value of an index W1 calculated by the following equation (IV) of not less than about 0.40,
X1=B1/A1xe2x80x83xe2x80x83(I)
Y1=D1/C1xe2x80x83xe2x80x83(II)
Z1=Y1xc3x97E1xe2x80x83xe2x80x83(III)
W1=Y1xc3x97E1xc3x97F1xe2x80x83xe2x80x83(IV)
wherein, as to the equation (I), A1 and B1 stand for respective half-widths of peaks, which are obtained by the process consisting of the steps:
(i) analyzing titanium oxide eight times according to an X-ray photoelectron spectroscopy,
(ii) obtaining an integrated spectrum of an electron state of titanium with respect to the above first analysis and the second analysis,
(iii) obtaining a half-width, A1, of a peak within a binding energy range of from 458 eV to 460 eV with respect to the integrated spectrum obtained in the above step (ii), and
(iv) carrying out the same steps as the above steps (ii) and (iii) with respect to the above seventh analysis and the eighth analysis to obtain a half-width, B1, of a peak, and as to the equation (II), C1 stands for an integrated value of absorbance within a wavelength range of from 250 nm to 550 nm in measurement of an ultraviolet-visible diffuse reflection spectrum of titanium oxide, and D1 stands for an integrated value of absorbance of titanium oxide within a wavelength range of from 400 nm to 550 nm;
as to the equation (III), E1 stands for a crystallite size of titanium oxide; and
as to the equation (IV), F1 stands for a degree of anatase crystallinity titanium oxide.
The present invention also provides titanium oxide having a value of an index V1 calculated by the following equation (V) of not more than about 0.97,
V1=H1/G1xe2x80x83xe2x80x83(V)
wherein, as to the equation (V), G1 and H1 stand for respective half-widths of peaks, which are obtained by the process consisting of the steps:
(i) analyzing titanium oxide four times according to an X-ray photoelectron spectroscopy,
(ii) obtaining an integrated spectrum of an electron state of titanium with respect to the above first analysis and the second analysis,
(iii) obtaining a half-width, G1, of a peak within a binding energy range of from 458 eV to 460 eV with respect to the integrated spectrum obtained in the above step (ii), and
(iv) carrying out the same steps as the above steps (ii) and (iii) with respect to the above third analysis and the fourth analysis to obtain a half-width, H1, of a peak.
Further, the present invention provides titanium oxide having a value of an index V1 calculated by the following equation (V) of not more than about 0.97, a value of an index U1 calculated by the following equation (VI) of not less than about 0.14,
V1=H1/G1xe2x80x83xe2x80x83(V)
U1=J1/I1xe2x80x83xe2x80x83(VI)
wherein, as to the equation (V), G1 and H1 stand for respective half-widths of peaks, which are obtained by the process consisting of the steps:
(i) analyzing titanium oxide four times according to an X-ray photoelectron spectroscopy,
(ii) obtaining an integrated spectrum of an electron state of titanium with respect to the above first analysis and the second analysis,
(iii) obtaining a half-width, G1, of a peak within a binding energy range of from 458 eV to 460 eV with respect to the integrated spectrum obtained in the above step (ii), and
(iv) carrying out the same steps as the above steps (ii) and (iii) with respect to the above third analysis and the fourth analysis to obtain a half-width, H1, of a peak; and
as to the equation (VI), I1 stands for an integrated value of absorbance within a wavelength range of from 220 nm to 800 nm in measurement of an ultraviolet-visible diffuse reflection spectrum of titanium oxide, and J1 stands for an integrated value of absorbance of titanium oxide within a wavelength range of from 400 nm to 800 nm.
The present invention still further provides a photocatalyst comprising titanium oxide mentioned above as a catalyst component.
In addition, the present invention provides a photocatalytic coating agent comprising said photocatalyst and a solvent.
Further scope of applicability of the present invention will become apparent from the detailed description given hereinafter. However, it should be understood that the detailed description and specific examples, while indicating preferred embodiments of the invention, are given by way of illustration only, since various changes and modifications within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.